In recent years, a transmission apparatus for an Optical Transport Network (OTN) or the like has been provided as a transmission apparatus (hereinafter, which may also be referred to as a node) designed for communication common carriers. Communication common carriers are requested to construct a network in which plural redundant paths (hereinafter, which may also be referred to as routes) are prepared to ensure a service availability so that even when one of the paths fails to operate and causes a communication inability, the service may continuously be provided by using another path. In addition, communication common carriers are requested to construct a network composed of a fewer facilities than ever so as to hold down prices for the provided service.
As a scheme for constructing the network responding to these requests, a shared mesh restoration scheme is proposed, for example. The shared mesh restoration scheme is a scheme where protection paths share a bandwidth, and resources for a recovery from the failure may be reduced, so that the high service availability may be realized at low costs.
As illustrated in FIG. 8, for example, 11 nodes including nodes 102A to 102K are coupled to each other via 12 links including links 104A to 104L on a network 100 based on the shared mesh restoration.
The network 100 sets a path passing through the nodes 102A, 102B, 102C, and 102D as a first working path and sets a path passing through the nodes 102H, 102I, 102J, and 102K as a second working path. The network 100 also sets a path passing through the nodes 102A, 102E, 102F, 102G, and 102D as a first protection path and sets a path passing through the nodes 102H, 102E, 102F, 102G, and 102K as a second protection path. The path passing through the nodes 102E, 102F, and 102G is a path shared by the first protection path and the second protection path.
According to the example of FIG. 8, communications on the first working path, the first protection path, the second working path, and the second protection path are respectively controlled by signaling messages 106, 108, 110, and 112. The respective nodes mutually transmit messages giving instruction information on securing the bandwidth or the like of the paths.
The respective nodes on the first working path and the second working path acquire the bandwidths requested by the corresponding signaling messages 106 and 110. The respective nodes on each of the paths perform setting of a data plane unit and activation of the path. The setting of the data plane unit includes setting of a line interface unit functioning as an input and output interface and setting of a cross connect unit that connects the respective line interface units. This allows user traffics to flow on the first and second working paths.
Since the first working path and the second working path pass through mutually different nodes and links on the network 100, the first working path and the second working path are not affected by the same link failure or the same node failure at the same time. In the case, bandwidths requested by the signaling messages 108 and 112 are reserved for the nodes on the first protection path and the second protection path, respectively.
Meanwhile, since a path passing through the nodes 102E, 102F, and 102G is shared by the first protection path and the second protection path, the bandwidth thereof is reserved. However, the setting of the data plane unit is not conducted at the nodes 102E, 102F, and 102G. This is because whether the shared nodes and links are utilized by the first protection path or the second protection path is not determined at a time before the occurrence of failure.
Here, it is assumed that a failure has occurred, for example, at the link 104L located between the node 102J and the node 102K on the network 100. For example, when an error is detected on the input and output interface connected to the link 104L, the node 102J determines that the failure has occurred at the link 104L and notifies the node 102H of failure information 114. When the failure information 114 is received, the node 102H switches the communication on the second working path to the communication on the second protection path. It is noted that the bandwidth has already been reserved on the second protection path, but the setting of the data plane unit has not yet been conducted.
The node 102H transmits the signaling message 112 for activating the second protection path so as to perform the setting of the data plane unit corresponding to the second protection path. When the nodes 102E, 102F, 102G, and 102K on the second protection path receive the signaling message 112, the data plane unit is set and validated at each of the nodes 102E, 102F, 102G, and 102K so that the reserved bandwidth may be utilized as the second protection path. The data plane unit is similarly set and validated at the node 102H. When the setting of the data plane units at the respective nodes on the second protection path is validated and the second protection path is activated, the user traffic starts to flow on the second protection path, and the service is recovered.
See Japanese Laid-open Patent Publication No. 2010-147932.
See also IETF RFC 4872, May 2007 and IETF RFC 3209, December 2001.